1. Field of the Invention
The present invention relates to a spray type ultrasonic washing apparatus, and more particularly to such ultrasonic washing apparatus using deaerated degassed washing liquid and keeping it in good deaerated condition on the way to work to be washed.
2. Description of the Prior Art
Ultrasonic washing apparatuses are widely used in washing work surfaces, deflashing work surfaces, etc.
Cavitation has been hitherto supposed to be easily formed in ultrasonic medium which is abundant in air bubbles.
The experiments performed by the inventor, however, revealed that to the contrary, cavitation can be easily formed in deaerated medium. This is because air bubbles in medium absorb energy of cavitation, thereby suppressing formation of cavitation. In contrast, when ultrasonic radiation is radiated in deaerated medium, a drastic pressure decrease will be caused under a certain condition, and when the deaerated medium pressure is lowered below saturated vapor pressure, the medium will be evaporated to form air bubbles, which will rapidly expand to form cavities. Then, they will be compressed to cause very high pressure, thereby expediting formation of cavitation.
For this reason use is made of deaerated medium in ultrasonic washing, and deaerated medium in which cavitation is formed, is sprayed against work to be washed.
This ultrasonic washing has the effect of reducing the time involved for washing works because deaerated medium permits effective formation of cavitation. Use of deaerated medium in the form of spray, however, permits invasion of air into the deaerated medium on the way to works to be washed. As a result the medium cannot remain deaerated, and the washing effect decreases with the decrease of cavitation.